A network of communication stations can share a communication medium (e.g., wires connecting multiple stations or a spectrum for transmitting radio signals among stations) using any of a variety of access techniques. Security for a shared communication medium network can be difficult since there is no protection from other devices that are connected to the shared medium. For example, two stations that are connected to a shared medium cannot communicate with each other in a secure manner without the danger of being subjected to snooping by other devices connected to the shared medium.